Peel and roughly dice the potatoes, shallots and celery.
Fry the shallot cubes in 20 g butter. Add the celery and potato cubes, season with nutmeg and add the remaining butter. Pour in the stock and cream, bring to the boil, season and simmer over medium heat until soft. Stir more often. Then stir through a liquor of Lotte (or pass through a sieve). Finally fold in truffle butter and season with salt, pepper and nutmeg.